In an LTE system, the synchronization (SYNC) signals and the broadcasting signals on the physical broadcast channel (PBCH) occupy a relatively narrow bandwidth (1.08 MHz) and are fixed at the center of the operation channel of a much wider bandwidth. The SYNC signals and information carried on the PBCH are crucial to system operation. The SYNC signals, generated based on Zadoff-Chu sequences, enable a mobile station to find the base station of the cell that the mobile station is in and to synchronize with the network. The PBCH carries critical system control information that a mobile needs to access the network. Since LTE is designed for use on a licensed spectrum, there is no need to consider interference originated from other systems (i.e., no inter-system interference). In this case, the fixed-location design of SYNC signals and PBCH is sufficient for the operation of the system.
Recently, the premium spectrum bands have been opened up by regulators for unlicensed use, especially TV channels that are now available due to switching from analogue to digital TV broadcasting. In an unlicensed environment, there may be considerably more interference from various sources. When used in such an environment, the fixed-location design of SYNC signals and PBCH such as in an LTE system may not cope well with interference. The SYNC signals and PBCH may be vulnerable in cases where a narrow-band interferer is present where the SYNC signals and PBCH are in frequency, as depicted in FIG. 1. As a result, performance of the system may be greatly degraded.